The invention relates to the field of power electronics. It relates in particular to a power semiconductor module as claimed in the precharacterizing clause of patent claim 1.
For high-power applications, power semiconductor modules are manufactured using press pack module technology. These press pack modules are used as high-power switches for currents of up to several thousand amperes in the high-voltage range up to 1000 kV. Since insulated gate bipolar transistors (IGBT), as are used nowadays in a press pack module, can withstand a voltage of only around a few thousand volts, a number of press pack modules are connected in series in at least one stack for a high-voltage switch. The stack, with up to several dozen press pack modules, is compressed with a force of around 100 kN.
A conventional press pack module, such as that described in EP 762,496, generally has a number of semiconductor chips which are arranged alongside one another and are mounted with a first main electrode on a base plate. Second main electrodes of the semiconductor chips are made contact with by a number of contact dies. The base plate is connected to a first main connection, and the contact dies are connected to a second main connection. The main connections may be in the form of disks, and may be interconnected by means of flanges. The contact die has spring elements, by way of example, which press against the individual chips.
The individual semiconductor chips in the press pack module are formed into several groups and are combined in units, so-called submodules, which can be prefabricated. In this case, the semiconductor chips are connected in parallel with one another, for example with one IGBT and one diode chip together in one submodule.
A press pack module such as this is described in the attached European Patent Application with the Application Number 01810539.5, and is illustrated schematically in FIG. 1. The figure is split into two halves, with the left-hand half showing one half of the module in the preinstalled state, and the right-hand half showing the other half of the module, in the installed state in a stack of three modules.
The module with the three illustrated submodules 2 is in this case pressed against an electrically and thermally highly conductive base plate 12, which, by way of example, may be a cold plate through which a cooling liquid flows.
Even in the preinstalled state, the submodules 2, which are introduced into the insulating housing 5 from above, have a spring stress applied to them and are pressed against the covering panel 11, which is firmly connected to the insulating housing. The spring stress is produced by spring elements in the individual submodules, and is transmitted to the first main connections 3. The second main connections 4 project downward out of the insulating housing 5, in order to ensure reliable contact with the base plate 12.
In the installed state, the second main connections 4 of the submodules are pressed into the interior of the module housing by means of a contact force that is exerted on the base plate and the covering panel. In the process, the spring elements are compressed, so that the contact force acting on the electrodes of the semiconductor chips in the interior of the submodules is increased. The insulating housing in this case ensures that the spring elements are not compressed excessively, so that the contact force does not become too great.
A stack with press pack modules extends over a length of several meters. Complex precautions are necessary in order to allow the pressure mentioned above to be exerted over such a length. It is thus desirable to increase the maximum blocking voltage per unit length in a stack, in order to manage with fewer press pack modules for a given voltage.
The height of the stack, and hence the costs associated with it, could be reduced by increasing the blocking voltage of individual press pack modules. Unfortunately there is scarcely any prospect of raising the maximum blocking voltage, as mentioned above, of power semiconductor chips with present-day technology.
The object of the present invention is thus to provide a power semiconductor module of the type mentioned initially, which has a greater blocking voltage per physical height unit.
This object is achieved according to the invention by a power semiconductor module having the features of patent claim 1.
The power semiconductor module according to the invention has at least two submodules between two main electrical connections which are arranged on mutually opposite, essentially parallel, main surfaces of the module. The submodules have two main electrical connections which are arranged on in each case one of two mutually opposite, essentially parallel, main surfaces of the submodules. The submodules comprise in each case at least one semiconductor chip, which has two main electrodes, which are electrically conductively connected to the main connections of the submodule. The submodules are arranged alongside one another, and one of their two main surfaces is pressed against the covering panel. At least two submodules are electrically connected in series.
In comparison to conventional press pack modules, the blocking voltage can be doubled or increased by several times by connecting two or more submodules, which are arranged alongside one another, in series.
This reduces the length and the costs of a stack, since fewer components, in particular fewer cooling elements, are required for the same blocking voltages.
The physical height of the power semiconductor module according to the invention is only slightly greater than that of conventional press pack modules. However, the additional increase in size leads to the module being more mechanically robust, and this is particularly advantageous in long stacks, in particular.
It is also possible to use better semiconductor chips, with a lower blocking voltage, in comparison to conventional press pack modules, for the same or greater blocking voltages. Since semiconductor chips such as these, with half the blocking voltage, together produce fewer losses than an individual semiconductor chip with the full blocking voltage, it is also possible to reduce the losses in conventional stacks with the same dimensions, by using power semiconductor modules according to the invention.
In a first embodiment of the power semiconductor module, the first main connection of at least one first submodule is electrically conductively connected to the covering panel. A first electrically insulating layer is arranged between the second main connection of the at least one first submodule and that main surface of the module which is opposite the covering panel, and a second electrically insulating layer is arranged between the first main connection of at least one second submodule and the covering panel. The second main connection of the at least one second submodule is electrically conductively connected to the second main connection of the module. The second main connection of the at least one first submodule is electrically conductively connected to the first main connection of the at least one second submodule, via a connection.
The submodules are electrically connected in series, so that the blocking voltage of the power semiconductor module with IGBT semiconductors is doubled.
In a second embodiment of the power semiconductor module, a first electrically insulating layer is arranged between the first main connection of at least one first submodule and that main surface of the module which is opposite the covering panel. The first main connection of the at least one first submodule is electrically conductively connected to the covering panel via a first connection. A second electrically insulating layer is arranged between the second main connection of the at least one first submodule and the covering panel, as well as between the first main connection of at least one second submodule and the covering panel. The second main connection of the at least one second submodule is electrically conductively connected to the second main connection of the module. The second main connection of the at least one first submodule is electrically conductively connected to the first main connection of the at least one second submodule via a second connection.
With the same alignment in the module, the submodules are connected electrically in series, back-to-back. Using IGBT semiconductors, this results in a four-quadrant power semiconductor module which can be switched off and is used, by way of example, as an alternating-current switch in a matrix converter.
Further exemplary embodiments and advantages can be found in the corresponding dependent claims.